Abstract: An improved single shell boiler is provided. The single shell boiler includes a closed vessel for containing a liquid heat transfer medium, with the liquid heat transfer medium having a surface. A first bundle of heat source tubes is located in the closed vessel and is adapted to be submerged within the liquid heat transfer medium for heating and vaporizing the liquid heat transfer medium. A second bundle of tubes is located in the closed vessel in a position which is adapted to be above the level of the liquid heat transfer medium within the vessel to receive heat by condensation of vaporized heat transfer medium on the second bundle of tubes. A condensate distribution plate is positioned between the first and second bundles of tubes. The condensate distribution plate is adapted to approximately evenly distribute condensate droplets released by the second bundle of tubes to break-up froth on the surface of the liquid heat transfer medium to enhance vapor release from the liquid heat transfer medium.